1. Field of the Invention
This invention relates to an elliptical vibrator apparatus which is used, for example, for handling parts such as bolts, nuts, and transistors.
2. Description of the Prior Art
In FIG. 1, an elliptical vibration parts-feeder is generally denoted by a reference numeral 1 and it is provided with a well-known bowl 2. A spiral track is formed in the wall of the bowl 2. A wiper as one of parts-orientating means is arranged at a suitable position of the down-stream side of the spiral track. The detail of the wiper is well-known and the drawing of the detail will be omitted. A flat plate is bent to form the wiper. The distance between the lower end of the flat plate and the track is larger than the thickness of a part to be handled in the bowl 2. But, it is smaller than the double of it. A posture-holding means is arranged at a discharge end portion of the spiral track. The parts of a predetermined posture are supplied through the posture holding means into a not-shown linear vibratory feeder as a next step.
The bowl 2 is fixed on an upper movable frame 7 as shown in FIG. 2. A similarly cross-shaped lower movable frame 8 as clearly shown in FIG. 3 is combined with four sets of vertical leaf springs 9 with the upper movable frame 7. Upper ends of the leaf spring 9 are fixed to the end portions 7a of the upper movable frame 7. The lower ends of leaf springs 9 are fixed to the end portions 8a of the lower movable frame 8. The end portions 7a and 8a are in alignment with each other in the vertical direction.
A vertical drive electro-magnet 11 is fixed at the central part of a stationary frame 10, facing to a central portion of the upper movable frame 7. A vertical movable core 13 is fixed to the lower side of the upper movable frame 7, facing to the vertical drive electro-magnet 11. A pair of horizontal drive electro-magnets 14a and 14b are fixed to side wall portions of the stationary frame 10 at both sides of the vertical drive electro-magnet 11. Electro-magnetic coils 15a and 15b are wound on the electro-magnet 14a and 14b. Horizontal movable cores 16a and 16b are fixed to the lower side of the upper movable frame 7, facing to the horizontal drive electromagnets 14a and 14b, respectively.
Four leg portions 17 are formed integrally with the stationary frame 10. The stationary frame 10 is supported through the leg portions 17 and vibration-absorbing rubbers 18 on the flour. Spring fixing portions 17a are formed integrally with the leg portions 17 as shown in FIG. 3. Leaf springs 19 are fixed to the spring fixing portions 17a as shown in the manner in FIG. 3. Both ends of the leaf springs 19 for the vertical drive are fixed to the spring fixing portions 17a by bolts B. The leaf springs 19 consist of two leaf spring elements which are superimposed through spacers 20 on each other. The central parts of the leaf springs 19 are fixed to the lower movable frame 8 by bolts B'.
In the above described arrangement, the horizontal drive electro-magnets 14a, 14b correspond to a first vibratory exciter for generating a horizontal exciting force. A first vibratory system to be driven by the horizontal electro-magnets 14a, 14b consists of the bowl 2, the leaf springs 9, the movable cores 16a and 16b, etc. The electro-magnet 11 correspond to a second vibratory exciter for generating a vertical exciting force. It consists of the bowl 2, the leaf springs 19, movable core 13, etc.
Generally, drive currents of the same frequency as the resonant frequency of the first (horizontal) vibratory system or nearly to the resonant frequency are supplied to the electro-magnets 14a, 14b and 11. Thus, the bowl 2 is vibrated at the resonant frequency F.sub.0 or nearly at the frequency f.sub.0 in the horizontal direction. The resonant frequency f.sub.1 of the second (vertical) vibratory system in the vertical direction is usually higher by a few percentages than the horizontal resonant frequency f.sub.0. As shown in FIG. 4, the phase difference between the force and vibrational displacement is equal to 90 degrees in the horizontal direction. That is clear from the vibration technology. The bowl 2 is vibrated at a different phase difference in the vertical direction. Thus, the bowl 2 is elliptically vibrated by the phase difference. The optimum phase difference between the vibrational displacements in the vertical and horizontal directions is theoretically equal to 60 degrees. In that case, the parts to be handled can be transported at the maximum transport speed on the track of the bowl 2. Accordingly, the phase difference is set to 90 degrees between the horizontal and vertical exciting forces. In other words, as clearly from FIG. 4, the resonant frequency in the vertical direction is equal to f.sub.1 and so the vertical vibration occurs behind the vertical vibration force by the phase of 150 degrees.
As clear from the vibration technology, when a vibratory system is driven at the resonant frequency, a little change of the load of the parts in the bowl 2 and a little fluctuation of the power source cause to change the resonant frequency of the vibratory system. Accordingly, even when the bowl is vibrated at the horizontal resonant frequency f.sub.0 and at the phase difference 90 degrees between the force and the displacement under no-load, the phase difference is varied with the fluctuation of the power source and the load of the parts. Accordingly, although the phase difference in the vertical direction changes little, it varies much in the horizontal direction. As the result, the phase difference between the vertical and horizontal vibrational displacements does not become equal to 60 degrees. Thus, the optimum vibrational condition cannot be obtained for the bowl 2.